A group of volunteers ate half a kilo of strawberries every day for two weeks to demonstrate that eating this fruit improves the antioxidant capacity of blood. The study, carried out by Italian and Spanish researchers, showed that strawberries boost red blood cells' response to oxidative stress, an imbalance that is associated with various diseases.
Scientists have previously tried to confirm the antioxidant capacity of strawberries using in vitro laboratory experiments. Now, a team of researchers from the Marche Polytechnic University (UNIVPM, in Italy) and the University of Granada (UGR, in Spain) have demonstrated this effect in vivo, in a study on human volunteers published in the journal Food Chemistry.
Each day, the scientists fed 12 healthy volunteers 500 grams of strawberries (of the 'Sveva' variety) over the course of the day. They took blood samples from them after four, eight, 12 and 16 days, and also a month later. The results show that regular consumption of this fruit can improve the antioxidant capacity of blood plasma and also the resistance of red blood cells to oxidative haemolysis (fragmentation).
"We have shown that some varieties of strawberries make erythrocytes more resistant to oxidative stress. This could be of great significance if you take into account that this phenomenon can lead to serious diseases," Maurizio Battino, lead author of the study and a researcher at the UNIVPM, said.
The team is now analysing the variations caused by eating smaller quantities of strawberries (average consumption tends to be a 150g or 200g bowl per day). "The important thing is that strawberries should form a part of people's healthy and balanced diet, as one of their five daily portions of fruit and vegetables," Battino points out.
"Various strawberry varieties are also being analysed in the laboratory, since they each contain antioxidants in differing amounts and proportions," explains José Luis Quiles, the Spanish participant in the study and a researcher at the UGR.
The body has an extensive arsenal of very diverse antioxidant mechanisms, which act at different levels. These can be cellular tools that repair oxidised genetic material, or molecules that are either manufactured by the body itself or consumed through the diet, which neutralise free radicals. Strawberries contain a large amount of phenolic compounds, such as flavonoids, which have antioxidant properties.
These substances reduce oxidative stress, an imbalance that occurs in certain pathologies, (such as cardiovascular disease, cancer and diabetes) and physiological situations (birth, aging, physical exercise), as well as in the battles between "reactive kinds of oxygen" -- in particular free radicals -- and the body's antioxidant defences.
When the level of oxidation exceeds these antioxidant defences, oxidative stress occurs. Aside from causing certain illnesses, this is also implicated in phenomena such as the speed at which we may age, for example.
Sara Tulipani, Josè M. Alvarez-Suarez, Franco Busco, Stefano Bompadre, Josè L. Quiles, Bruno Mezzetti, Maurizio Battino. Strawberry consumption improves plasma antioxidant status and erythrocyte resistance to oxidative haemolysis in humans. Food Chemistry, 2011; 128 (1): 180 DOI: 10.1016/j.foodchem.2011.03.025
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